Lymphatic drainage patterns of a hybrid radioactive and fluorescent tracer for sentinel node procedures: A validation study using lymphoscintigraphy and SPECT/CT

Objectives To compare the lymphoscintigraphic drainage patterns of the European gold standard 99mTc-nanocolloid to a novel hybrid radioactive and fluorescent tracer (ICG-99mTc-nanocolloid).

Methods 25 patients with either a melanoma in the head and neck region (10), on the trunk (6), or with penile carcinoma (9) scheduled for sentinel node (SN) biopsy were included. First, the standard 99mTc-nanocolloid lymphoscintigraphic procedure was performed, followed by SPECT/CT. The same afternoon (n=10), or the next morning (n=15), this scintigraphic procedure was repeated using ICG-99mTc-nanocolloid. The images of both injections were evaluated and count rates in the SNs were calculated. SNs were surgically localized using blue dye, a gamma ray detection probe, a portable gamma camera and a fluorescence camera.

Results Lymphatic drainage was visualized in all 25 patients using 99mTc-nanocolloid (66 SNs). The same SNs were identified during the second scintigraphic procedure with ICG-99mTc-nanocolloid. A high correlation between the radioactive counts rates in the SNs of both scintigraphic studies was observed (mean R2 = 0.83). Intraoperatively, all preoperatively identified SNs could be localized using radio- and fluorescence guidance combined. 95% of the SNs could be intraoperatively visualized with fluorescence imaging, while merely 54% stained blue.

Conclusions The lymphatic drainage pattern of hybrid ICG-99mTc-nanocolloid is identical to that of 99mTc-nanocolloid. This observation and the addition of intraoperative fluorescence guidance warrant wider application of ICG-99mTc-nanocolloid for SN procedures